When we vacation at Disney, we do the dining plan. Having
DVC is not going to change the fact that we don't like cooking on vacation, and the DDP does still save us a little bit of money (believe me, I make the calculations after every trip just to confirm). I like the conveninece of prepaying our meals ahead of time, and I find it a wonderful luxury to eat dessert with every meal - - that just screams vacation to me. I will say, however, that when we went to Disney in September, 2008 for 9 days, by about day 6 we were really getting tired of having Captain Cook's for our breakfasts and lunches...everything we ordered from there really did start tasting the same. When doing extended stays in the future, we will definitely branch out a little bit (eat at the parks, other resorts, etc.) so we don't fall into a rut again.
ETA: To the OP, since you will be staying off site for a couple days, you could use the opportunity to dine at a couple of Disney's signature restaurants since you'll have excess credits. Just something else to think about.
Good luck!